Spence 9412146 A three year program of research is proposed of atomic bonding in crystals, at interfaces and at defects. Ceramics and intermetallic compounds will be studied using a combination of ab-initio quantum molecular dynamics computations, self-consistent calculations and experimental measurements of bond charge distributions by quantitative convergent beam electron diffraction method. The Zeiss Omega energy-filtering electron microscope at the Arizona State University center for High Resolution Electron Microscopy will be used for the experimental work. Principal Investors propose a new technique based on the specular electron beam reflected from a metal-ceramic interface in the transmission geometry for reflection imaging, microanalysis and bonding studies of buried interfaces. This work is collaborative with C.P. Flynn. For perfect crystals, in which bonds have been "seen" for the first time only recently, Principal Investors propose bond charge distribution measurements in titanium-aluminum and a series of ionic crystals in order to test the accuracy of self-consistent computations based on the local density approximation. Measured bond distributions will be compared for titanium-aluminum with and without manganese doping, which is found to reduce brittleness. In ferroectric crystal Principal Investigators plan comparisons of charge transfer between titanium and oxygen in strontium titanate and isostructural barium titanate oxygen in order to understand why one is ferroelectric and the other not. %%% The proposed research seeks to investigate the origins of atomic bonding in crystals, at interfaces and defects. Ceramics and intermetallic compounds will be studied using a combination of theoretical calculations and experimental measurements of bond charge distributions by quantitative techniques. ***
